This invention relates to an apparatus for shaping workpieces, for example, U.S. 2xc3x974 inch timbers, with rounded ends especially for use as web members for trusses, being particularly concerned with an apparatus for cutting workpieces to such length as may be called for, and shaping the ends of workpieces to rounded form.
As is well known, timber roof trusses, such as Fink, Howe and Queenpost trusses, comprise upper and lower chords with web members extending therebetween triangulating the space between the chords, the chords and web members being fastened together by nailing plates. In much of the truss construction in the past, the webs have been fabricated with each end cut off straight at the requisite angle for engagement of the respective end flush with the respective chord (i.e. mitered). This has entailed a great deal of sawing with the requirement for cutting at different angles and the problem of organizing the cut timbers according to the mitering angles.
There has been a recent trend toward using webs with rounded ends instead of mitered ends, enabling the webs to be assembled in a truss extending at any of a wide range of angles with respect to a chord, in firm contact at a rounded end thereof with a chord. This has led to the desirability of manufacture of webs (e.g. 2xc3x974 timbers) with both ends rounded (i.e. of generally semi-circular conformation) at a relatively high rate of production and at relatively low cost for realization of cost savings in truss manufacture.
Some devices for shaping workpieces, such as timbers, include a feeding system which delivers workpieces to a queue, or loading position, from where they are inserted one at a time into an aligned, horizontal row arrangement. An advancing mechanism advances the row of workpieces along a track leading toward a saw or other shaping tool. Upon each advance, the row is indexed downstream and one new workpiece may be received from the feeder into the row. Typically, the feeder operates in continuous motion (e.g., a constantly moving conveyor) while the advancing mechanism operates in reciprocal or cyclic motion and, consequently, the feeder and advancing mechanism are separately driven and independently powered. For example, the feeder is powered by an electric motor, while the advancing mechanism features hydraulically powered actuators with associated hydraulic reservoir and hoses. Unfortunately, that dual drive results in increased cost and complexity.
A second drawback relates to the shaping tool which rounds ends of workpieces to a semi-circular form. That tool is typically a rotatable, two-dimensional profile bladed cutter which includes upper and lower cutting blades for removing material from tops and bottoms of the ends, but not from central regions. The blades have shapes which, when cutting a workpiece, impart forces on the workpiece in a direction transverse to its intended path of motion. Consequently, the workpiece has a tendency to move laterally outward, away from the aligned row of workpieces and into a position between the upper and lower blades where it collides with a hub of the tool or other part. That causes the machine to jam and results in costly downtime.
Accordingly, among the several objects of the invention may be noted the provision of an apparatus for forming workpieces with rounded ends at a relatively high rate of production and at relatively low cost; the provision of such an apparatus which has a drive system common to both feeding and indexing workpieces toward a cutting tool; the provision of such an apparatus which prevents lateral movement of a workpiece while being cut by the cutting tool; the provision of such an apparatus for production of workpieces of different lengths; and the provision of such a method and apparatus for reliable and economical rounded-end truss web member production.
In general, an apparatus of the present invention shapes an end of a workpiece as the workpiece is advanced along a path of travel. The apparatus comprises a frame defining the path of travel for the workpiece, and a rotary cutter positioned laterally adjacent the path for engaging the workpiece as it moves along the path. The cutter has a hub with upper and lower cutting arms extending outwardly from the hub for shaping upper and lower portions, respectively, of the end of the workpiece. The cutting arms have arcuate cutting edges and generally define a concave recess spaced between the upper and lower arms. A stop bar is mounted on the frame for preventing movement of the workpiece in a direction generally transverse the path of travel while the cutter is shaping the end of the workpiece. The stop bar is positioned adjacent to the path of travel and configured for engagement by the end of the workpiece if the workpiece should move in the transverse direction. The stop bar has a downstream end which extends into the concave recess of the cutter without contacting the cutter for supporting the workpiece against lateral movement while the workpiece is being cut by the cutter.
In another aspect, a feeding system of the invention is for feeding workpieces into a row of workpieces arranged along a path of travel and cyclically advancing the row along the path toward a downstream cutting machine. The system comprises an elongate frame defining the path of travel, the path having an upstream end and a downstream end. A conveyor is on the frame for receiving the workpieces thereon and delivering each workpiece sequentially to a loading position adjacent the upstream end of the path of travel. A pushing device is at the upstream end of the path. The pushing device is cyclically movable between an extended position wherein the pushing device engages a workpiece at an endmost upstream position of the row to lengthwise advance the row of workpieces along the path in the downstream direction, and a retracted position wherein a workpiece at the loading position may be deposited into the row at the endmost upstream position. A drive is for simultaneously driving the conveyor and the pushing device. The drive is operatively connected to the conveyor for moving the conveyor continuously in generally unidirectional motion and operatively connected to the pushing device for moving the pushing device in reciprocating motion between the extended and retracted positions for moving the workpieces along the path.
In yet another aspect, apparatus of the present invention is for feeding workpieces into a row of workpieces arranged along a path of travel and advancing the row along the path to a cutting machine for shaping the workpieces. The apparatus comprises a frame, the cutting machine, and a conveyor on the frame for receiving the workpieces thereon and delivering each workpiece sequentially to a loading position adjacent an upstream end of the path of travel. A pushing device is at the upstream end of the path comprising a slidably mounted bar, a connecting rod connected to the bar for moving the pushing device in reciprocating motion, and a disk having an offset crank pin attached to the connecting rod for movement. The pushing device is reciprocal between an extended position wherein the bar engages a workpiece at an endmost upstream position of the row to lengthwise advance the row of workpieces along the path in the downstream direction and through the cutting machine, and a retracted position wherein a workpiece at the loading position may be inserted into the row at the endmost upstream position.
Other objects and features will be in part apparent and in part pointed out hereinafter.